Generator pilot raising device



July 12, 1932. F. F. BUNTS ET AL GENERATOR PILOT RAISING DEVICE Filed July 3, 1929 Patented July 12, 1932 TED ATE PATENT OFFICE" FRANK F. BUNTS, OF MONROE, AND WARREN E. ROGERS, OF TRENTON, MICHIGAN GENERATOR PILOT RAISING DEVICE Application filed July 3, 1929. Serial No. 375,840.

This invention relates tobrush liftingdevices for electric generators and has for its object to provide a device for lifting the pilot brushes out of operative relation with the armature during normaloperation of the generator to which they are attached.

A further object is to provide a device of the type described which will be automatic to relieve the pilot brushes from further duty as quickly as the running brushes shall have been lowered to operative position.

The pilot brushes of a generator present a comparatively small surface to the commutator so that a strong and positive pressure is required to establish proper electrical contact. The result is that if the pilot brushes remain in operative position during normal operation of the generator a groove is worn in the surface of the commutator and the brushes are also quickly worn away without having supplied a corresponding amount of useful work.

It is, therefore, a specific object of this invention to provide a simple mechanism 25 which will operate to raise the pilot brushes out of operative position as quickly as the running brushesshall have attained their position for normal operation by a lever arrangement which will positively maintain the 3o pilot brushes in an elevated position where they will require no further attention and in such manner that they will again assume an operative position upon the lifting of the running brushes thereby automatically estabthe generator shall be stopped.

Among other objects are included simplicity of structure, relative cheapness in the cost of manufacture, reliability and neatness of design.

Still further objects either directly result- 1 '60 c Figure 1 is a side elevation ofour improved lishing a correct starting position each time i device together with such brushes of a generator as will aid the description thereof;

Figure 2 is a side elevation of the device which may be considered as a section taken along line 2" X of Figure 1.

Referring more particularly to the drawing, numeral 1 refers to a brush support which carries a rock shaft 2 rotatable around "port whichis always of some form to lower and elevate the running brushes of a generator, it being understood that the brushes are normally elevated out of contact with the commutator of the generator during starting and are lowered bysome means as, for instance, a rock shaft for contact therewith after the armature has attained a synchronous or desired speed ofrotation.

For starting, at least one pilot brush 9 is used in assisting the generator to build up.

These provide a connection for indicating.

polarity and through them the exciting current is permitted to flow, whereby the field of the machine may be built up. After the converter or generator has been synchronized and the polarity checked the starting switch (not shown) may be thrown to the running position and the brushes lowered on the cominutat or as illustrated at 9a by actuation of the rockshaft Qas will be well understood by those skilled in the art. In the presentinstance, this pilot brushis pivotally attached to a link-10 which is keyed to a bent arm 11 on which pressure is applied to form a good con vtact between the pilot brush and the armature, by means of a spring 12. This arm 11..

is mounted to slide through guideways in two ears 13 extending outwardly from" a back plate l l placed here for that purpose and also for the purpose of providing a support for an upper ear 15, the purpose 0 p which will appear later. The back plate 14 isrigidlyse- I cured to an extension 16 rigidly attached to I the plate 1 for that purpose.

The arm 11 comprises the lower bent portion heretofore mentioned, and a link 17 pivotally secured to the upper end thereof. lhis link 17 is adjustable as to length in any conventional manner, and has pivotally attached to the upper end thereof an extension 18 which comprises a core for and carries a seat for the spring 12. The upper end of the extension 18 is guided in an eye through another upper ear 19 of the back plate 14.

Upon the pivot pin connecting the link 17 and the extension 18 there is mounted an arm 20 which is also pivotally mounted on the ear 15. This arm is bent at its outer end to form a right angle, the bend being made so that the outer end 21 of the shaft 1 will strike it and depress the outer end of the arm 20 upon rotation of the rock shaft for the purpose of lowering the brushes 8. Such depression of the outer end will, of course, raise the inner end which will in turn raise the arm 11 and the brush 9. An indicator 22 may be attached to the bent end of the arm 20 for cooperation with graduations 28 to indicate the position of the pilotbrushes. Ths will be advantageous in structures where housings or other equipment prevent the pilot brushes from being seen by an operator.

It will thus be seen that upon starting, the pilot brushes will be in a position to take the flow of exciting current to assist the generator in building up and after the commutator has attained synchronous speed the rockshaft 2, either by manual or automatic means, will rock to lower the running brushes.

During this rocking, the end 21 of the shaft h 4 will strike the end of arm 20 raising the arm 11 and consequently the pilot brush 9. It is likewise seen that a raising of the running brushes 8 will also raise the end of the shaft 1 which will relieve the compression on the spring 12 so that the pilot brushes will be urged against the commutator pending further starting.

It will be seen that one object of the invention as revealed in the drawing is simplicity and that many modifications may be made without departing from the spirit of our invention, and we, therefore, desire to be limited in the application and construction thereof only by the scope of the appended claims,

wherein:

What we claim is:

1. In combination with the commutator of V ning brushes upon rocking of said rock shaft, ,7

a connecting link for each of said brushes, an arm pivotally mounted on the connecting link of said pilot brush and on a fixed support, rocking of said rock shaft for lowering said running brushes causing said shaft to depress said arm whereby said pilot brush is raised and yieldable means associated with said pilot brush to return said brush to contact with said commutator upon withdrawing said shaft from contact with said arm.

2. The combination with a commutator, a main brush and an auxiliary brush cooperable with said commutator of means for alternately raising said brushes so that when one brush is in engagement with the commutator the other will be out of engagement, consisting of a rock shaft interconnecting said brushes for causing one to be lowered while the other is being raised.

3. In a converter, the combination with a main brush and an auxiliary brush of means for alternately raising one of the brushes and lowering the other brush. said means com- 

